JPH0132700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser scanning deflection device that can be applied to an image recording device or the like that performs recording using laser light and achieves excellent effects.

Recently, an image recording device using a laser beam that combines electrophotography technology and laser exposure technology has been developed. This device has features such as high speed recording, high resolution, and no noise, and is attracting attention as a device for laser printers and the like.

Although image recording devices using laser light have extremely excellent performance as described above,
Currently, the biggest obstacles to putting this type of device into practical use are the technical difficulty of the components and their high cost. Recently, semiconductor lasers have been put into practical use as laser light sources instead of gas lasers, and the cost of devices has been reduced by taking advantage of their advantages such as small size, low cost, and self-modulation. However, the laser optical system still requires special equipment, and the following two elements make the entire equipment extremely expensive and special.

One of them is a rotating polygon mirror that scans and deflects the laser beam. In order to maintain the precision of the laser beam, the tilting precision of each face of the polygon mirror must be within a few seconds, which requires high-precision processing technology. Also, high-speed rotation requires advanced bearing technology.

The other is the Fθ lens, which focuses the beam polarized by the rotating polygon mirror onto the photoreceptor. In a normal condensing lens, the speed at which the photoreceptor is scanned differs at the periphery, causing distortion due to the speed of the image, so this lens corrects this distortion.
Fθ lenses are special lenses with large apertures that require advanced technology to design and polish, and are expensive.

Instead of using such a special optical system, it is conceivable to polarize the laser beam using a micromirror (hereinafter, a galvanometer mirror will be explained as an example) that deflects the beam at an angle corresponding to the electric signal. However, it is extremely difficult to swing a galvano mirror in a sawtooth waveform at high speed. The optimal method for driving a galvano mirror is to cause the reflecting mirror to resonate with a sine wave and deflect it, which allows stable driving at high speed. However, when this deflection method is used, since the scanning speed is different between the central part and the peripheral part of the photoreceptor, there are drawbacks such as distortion of the recorded image and difference in the amount of laser exposure at the peripheral part.

The present invention provides a laser scanning deflection device that does not require any special technology or elements and is constructed using common parts, which greatly contributes to practical application and is also inexpensive. . That is, in the present invention, a two-beam semiconductor laser is used, one laser beam is used for image recording (or image reading), and the other laser beam is used for a synchronization signal to correct image speed distortion. It is characterized by the use of a high-speed micromirror driven in a sinusoidal manner and an ordinary focusing lens, making it possible to significantly reduce the cost of the entire device. An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment in which the laser scanning deflection device of the present invention is applied to an image recording device. Note that the present invention can be similarly applied to an image reading device using a laser beam, which will be described later.

In Figure 1, 1 is a two-beam semiconductor laser with two laser emitting parts integrated on a substrate, one laser beam (broken line) is used for recording images, and the other laser beam is used for synchronization signals (solid line). used as. Each laser beam is focused and parallelized by a collimator lens 2 and deflected by a galvano mirror 3. The recording laser beam is imaged on the surface of the photoreceptor 5 by an ordinary focusing lens 4, but the synchronizing signal laser beam is reflected and separated by a reflection mirror 6 installed in front of the photoreceptor 5.
Next, the light-shielding stripes are selectively reflected by equally spaced reflecting plates 7 and detected by a laser photodetector 8 as a pulsed signal with a frequency proportional to the beam deflection speed.

The pulse signal S from the laser photodetector 8 is converted to a voltage V by a frequency voltage converter (hereinafter referred to as FVC) 9.
This voltage is converted into a voltage controlled oscillator (hereinafter referred to as
It is given as a bias current to the frequency control voltage of VCO) 10 and the laser drive of the laser modulation circuit 11.

FIG. 2 shows the signals of each part of the speed distortion correction circuit.
Since the galvanometer mirror 3 is driven in a sinusoidal manner, the scanning speed is fast at the center and slow at the periphery. Since light-shielding stripes are arranged at regular intervals on the reflection plate 7, a pulse signal S having a frequency proportional to the scanning speed is obtained from the laser light detector 8 for synchronizing signals.
The signal V converted into a voltage proportional to the speed by the FVC 9 is used for the following two corrections.

One is image distortion correction, in which the voltage of the VCO 10 is controlled to correct the modulation clock signal F.
That is, the modulation clock signal is controlled in proportion to the speed,
Correct the image to a certain level. The signal from the laser photodetector 8 may be used as the modulated clock signal F.
In this case, if the resolution of the image is 100 .mu.m, the interval between the light-shielding stripes must also be 100 .mu.m.
It is also practical to use a method in which the light-shielding stripes are set at a pitch of 500 μm and the frequency is increased five times using a circuit such as a VCO, and an example of this is shown in FIG. This method is particularly effective when a slit plate is placed in place of the light-shielding stripes and the transmitted light from the laser beam is detected, since it is difficult to create long and narrow slits with a pitch of 100 μm. It is also effective to use the light-shielding striped reflector 7 as the reflection mirror 6, since the synchronizing signal laser beam is shifted to the front of the imaging point, thereby increasing the beam diameter.

The other is correction of laser light output. Since the galvanometer mirror is driven in a positive arc waveform, the scanning speed of the recording laser beam on the photoreceptor is faster at the center and slower at the periphery, so the amount of exposure at the center decreases and the image becomes thin or pale. Therefore, the laser output can be controlled and corrected using a voltage V proportional to the scanning speed of the laser beam. FIG. 3 shows an example in which the driving bias current of the semiconductor laser is changed in proportion to the correction voltage V to correct the laser output. In the figure, 20 indicates the characteristics of the drive current and laser output of the semiconductor laser. When the scanning speed is slow, the bias shown in 21 is added, and when the scanning speed is fast, the bias shown in 22 is added, and the laser output is increased by 2.
3, 24, and the output can be corrected. The correction amount of the bias current is adjusted so that the image distortion remains constant.

FIG. 4 shows an embodiment of an optical path using a semiconductor laser having two laser beams. If the distance between the two semiconductor lasers 12 and 13 is Δy, and the focal lengths of the collimator lens 14 and the focusing lens 15 are f ₁ and f ₂ , respectively, then the distance y between the two laser images on the imaging plane is as follows: When Δy is small, Then, it is shown as y=f ₂ /f ₁ ·Δy. Δy is set to 100 μm to 300 μm in order to eliminate the influence of aberrations due to optical axis deviation of the collimator lens. If f ₁ = 10mm, f ₂ = 250mm, y = 25 ~ 75
mm, and by inserting a reflecting mirror 16 in front of the photoreceptor 19, it becomes possible to separate only the synchronizing signal laser beam. Further, a light-shielding striped reflection plate 17 is placed at a position corresponding to the focal plane of the synchronizing signal laser beam, and a laser light detector 18 is provided afterward to extract a synchronizing signal with a frequency proportional to the scanning speed of the laser beam. If the area of the laser photodetector 18 is small, a method is used in which the laser beam is focused using a parabolic mirror.

Although the above embodiment describes an image recording device, the laser scanning deflection device of the present invention can be similarly used in an image reading device.

As described above, according to the laser scanning deflection device of the present invention, a semiconductor laser having two beams is used,
One laser beam can be used for the synchronization signal to correct the image speed distortion caused by the deflector, and in particular, the semiconductor laser drive bias current is changed according to the scanning speed of the laser beam for the synchronization signal to read the data. In addition, since the output level of the laser beam for recording is controlled, accurate reading and recording without uneven printing can be performed, and recording devices that use laser beams will greatly contribute to the practical application of reading devices. be.

[Brief explanation of drawings]

Fig. 1 is a main part configuration diagram showing an embodiment of an image recording device to which the laser scanning deflection device of the present invention is applied, Fig. 2 is a waveform diagram showing signals of the scanning speed distortion correction section, and Fig. 3 is a bias current diagram. FIG. 4 is a diagram showing the relationship between the output of the laser beam and the output of the laser beam, and FIG. 4 is a configuration diagram of the main part. DESCRIPTION OF SYMBOLS 1... 2-beam semiconductor laser, 2... Collimator lens, 3... Galvano mirror, 4... Concentrating lens, 5... Photoreceptor, 6... Reflection mirror, 7...
Light-shielding striped reflector, 8... Laser photodetector, 9... Frequency voltage converter (FVC), 10... Voltage controlled oscillator (VCO), 11... Laser modulation drive circuit.

Claims (1)

[Claims] 1. A two-beam semiconductor laser light source having two laser emitting parts, a deflection means for deflecting two laser beams for control and reading or recording from the semiconductor laser light source, and a deflected laser beam for reading or recording. a scanning surface on which the laser beam is focused and an image is read or recorded; a detection means for separating only the deflected control laser beam and detecting the scanning speed of the laser beam; and a detection means for detecting the scanning speed of the laser beam; a first control means for controlling the modulation speed of the laser beam for reading or recording; and a first control means for controlling the modulation speed of the laser beam for reading or recording; A laser scanning deflection device comprising: second control means for controlling an output level.